Terry Bowman, 59, said she had seen her husband, a member of the Harford County sheriff's office, get hurt during the unrest that swept Baltimore in April after the death of Freddie Gray.
"I'm here to show respect," she said. "I'm here to show that I feel strongly."
Police morale sank after six officers were charged in connection with the death of the 25-year-old Gray, who suffered fatal injuries after being arrested in April and transported to the Western District station. On Thursday the police union said in a statement that its members fear being held criminally responsible even if they take steps to enforce the law in good faith.
Amid lingering tension and plummeting arrest rates, violence has spiked across the city, and in May 40 people have been killed in Baltimore, the deadliest month since 1990. Many of the demonstrators questioned why those deaths have not attracted the same level of outrage as Gray's.